1. Field of the Invention
The present invention relates to the field of semiconductor components and more specifically medium to high power components.
2. Discussion of the Related Art
In this field, components meant to be arranged in series with a load and having a function of limiting a current in the load to a maximum predetermined value are known. For this purpose, a MOS depletion transistor having its gate connected to its source, for example, is used. Components operating as circuit-breakers also are known.
Unpublished French patent application No. 95/15508 of Dec. 20, 1995, filed by the present Applicant, describes a static and monolithic component operating both as a current limiter and as a circuit-breaker. Such a component allows a current with a limited value to flow through, so long as a voltage at its terminals does not exceed a predetermined triggering threshold, and interrupts the current flow beyond the triggering threshold. This component is self-restarting, that is, it resumes operation as a current limiter again as soon as the voltage at its terminals goes below a predetermined triggering threshold.
The component of the above-referenced French application exhibits an operational characteristic as shown in FIG. 1. As long as the voltage at its terminals is lower than a switch-off voltage VD, the current is limited to a substantially constant value Ion. As soon as the voltage across the component exceeds the switch-off voltage VD, the current falls to a break current value Ioff which is lower with respect to Ion, whereby the current through the circuit including the component is substantially interrupted.
The above-mentioned French application provides two architectures to reach the desired result, shown as blocks in FIGS. 2A and 2B.
The component of FIG. 2A is meant to be connected between terminals A and K, a first terminal or anode terminal A being positive with respect to a second terminal or cathode terminal K. It includes, between these two terminals A, K, a current limiter 1 and a voltage sensor 2. The voltage sensor is, for example, a voltage divider which supplies, on a terminal C, a control voltage VC when the voltage between terminals A and K reaches the switch-off value VD. The control voltage VC controls current limiter 1 to inhibit its operation, that is, to make it blocking.
In the embodiment illustrated in FIG. 2B, voltage sensor 2 turns off a switch 3, in series with limiter 1, when the voltage between terminals A and K reaches switch-off value VD.
The above-mentioned French patent application describes embodiments of the voltage sensor wherein the sensor comprises a voltage divider 2 including two depletion N-channel MOS transistors connected in series and operating as non linear resistors. Each of these MOS transistors has its gate connected to its source.
It is indicated that, during cut-off phases, break current Ioff mainly corresponds to the current through detector 2.
This non-zero break current often is not a disadvantage for the desired function, so long as it is low enough, since it can in particular be used as a detection signal after the triggering of the circuit-breaker.
However, it is desired in some applications to have a break current Ioff with a zero intensity, and this all the more as, beyond voltage VD, conversely to what is schematically shown in FIG. 1, current Ioff increases with the voltage.